1. Field of the Invention
The present invention relates to a chopper folder for a rotary press for folding signatures periodically conveyed from a folding machine of a rotary press, and more specifically to a chopper folder equipped with a blade for pushing a signature into a space between a pair of folding rollers in order to fold the signature parallel to the conveyance direction.
2. Description of the Related Art
Conventional chopper folders have employed various schemes in order to move a chopper blade; e.g., a scheme in which a chopper blade is moved along an arcuate path and a scheme in which a chopper blade is moved along a linear path. In recent years, in order to cope with increased operation speed of rotary presses, the linear motion scheme—which can reduce the inertia of a movable portion—has been employed in many cases. Techniques in relation to such a linear motion scheme are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 6-199471, Japanese Patent No. 2983247, and Japanese Utility Model Application Laid-Open (kokai) No. 5-22446.
In the apparatus (Conventional Apparatus 1) disclosed in Japanese Patent Application Laid-Open No. 6-199471, two planetary gear mechanisms are disposed adjacent to each other. One of the planetary gear mechanisms has a first rotary shaft which rotates about its own axis, while revolving about a first center line. The base end of a first arm is fixedly connected to the first rotary shaft; and the distal end of the first arm is rotatably coupled to one end portion of a chopper blade. The other planetary gear mechanism has a second rotary shaft which rotates about its own axis, while revolving, in the direction opposite the above revolving direction, about a second center line parallel to the first center line. The base end of a second arm is fixedly connected to the second rotary shaft, and the distal end of the second arm is rotatably coupled to the other end portion of the chopper blade. Gears formed on the respective outer circumferential portions of respective disks of the two planetary gear mechanisms are meshing-engaged in order to form a paired mechanism.
Opposite longitudinal ends of an upper edge of the chopper blade, which is a far-side edge with respect to a conveyance plane along which signatures are conveyed, are supported via bearings by means of shafts provided at the respective distal ends of the first and second arms.
Each of the planetary gear mechanisms has the following configuration. A cylindrical main gear having gear teeth on its outer circumferential portion is fixed to a frame to be aligned with the corresponding center axis. A rotary center shaft is passed through a hollow of the cylindrical main gear. An intermediate gear in meshing engagement with the main gear and a small gear in meshing engagement with the intermediate gear are rotatably attached to the corresponding disk. The small gear is fixed to the corresponding rotary shaft to be integral with the corresponding arm.
When the first and second rotary shafts are simultaneously revolved in opposite directions about the first and second center axes, respectively, the chopper blade is moved upward and downward by the first and second arms. In order to cancel out dynamic imbalance forces generated in the vertically moving chopper blade to thereby create a balanced state, a counterweight is attached to each rotary shaft on the opposite side of the corresponding arm. One of the rotary center shafts rotatable about the respective center lines is rotated by means of drive torque transmitted from the folding machine via a belt. The disks are integrally fixed to the end portions of the rotary center shafts to be integral therewith. The disks rotate while maintaining engagement between gears provided on the outer circumferential portions of the disks.
Each of the planetary gear mechanisms operates as follows. When the rotary center shaft is rotated, the disk is rotated, so that the intermediate gear supported by the disk and being in meshing engagement with the main gear is rotated, and the small gear supported by the disk and being in meshing engagement with the intermediate gear is rotated. As a result, the intermediate gear and the small gear revolve about the center line, so that the arm fixedly connected to the small gear rotates about the rotary shaft, together with the counterweight. Thus, the chopper blade is moved upward and downward by the arm.
In the apparatus (Conventional Apparatus 2) disclosed in Japanese Patent No. 2983247, two linear-feed crank mechanisms are connected to opposite longitudinal ends of a chopper blade. Each linear-feed crank mechanism includes two crank members having the same arm length and two links having the same length. The crank members are arranged in the longitudinal direction of the chopper blade and are rotated in opposite directions. The upper ends of the links are coupled to the respective crank members via pins. The lower ends of the links are coaxially coupled to the upper end of the corresponding longitudinal end of the chopper blade via a pin. Rotary shafts of all the crank members of the two linear-feed crank mechanisms are supported by the gear box.
One of the rotary shafts of the two linear-feed crank mechanisms is rotated by a motor connected directly to the rotary shaft or a drive unit of the folding machine. As a result, gears which are provided on the rotary shafts of the two linear-feed crank mechanisms and which are in direct meshing engagement with one another rotate, so that the linear-feed crank mechanisms operate in order to move the chopper blade upward and downward.
The apparatus (Conventional Apparatus 3) disclosed in Japanese Utility Model Application Laid-Open No. 5-22446 includes a reciprocal linear motion unit which is connected to the widthwise center of a chopper blade with respect to the conveyance direction of signatures and reciprocates the chopper blade linearly; and a guide portion for guiding the chopper blade along the direction of reciprocal linear motion. Specifically, a crank pin of a planetary gear box serving as a reciprocal linear motion unit is rotatably connected to the widthwise center of the chopper blade. Further, guide bars are fixed attached to the opposite widthwise end portions of the planetary gear box; and bearings fixed to the opposite widthwise ends of the chopper blade are supported by the guide bars such that the chopper blade is movable in the vertical direction.
The pitch circle diameter of a small gear provided in the planetary gear box is half the pitch circle diameter of an internal gear fixed to the planetary gear box. Further, the crank radius of a crank fixed to the shaft of the small gear is half the pitch circle diameter of the small gear.
Therefore, when the small gear in meshing engagement with the internal gear moves, theoretically, the crank pin moves linearly. However, in actuality, the crank pin reciprocates vertically, while swinging horizontally, along a lip-shaped arcuate path. Therefore, a hole which is formed in the chopper blade in order to receive the crank pin is elongated in the direction perpendicular to the direction of movement of the crank pin, to thereby prevent excessive force from acting on the chopper plate in the longitudinal direction as a result of swing motion of the crank pin.
The above-described Conventional Apparatus 1 has the following drawbacks.
(1) Due to employment of two planetary gear mechanisms, the structure becomes complex, and a large number of gears, which require some backlash, must be used as structural components. Therefore, highly precise machining and assembly are required. In addition, the overall size of the apparatus becomes large as a result of the large stroke of the chopper blade, and manufacturing cost is high.
(2) Imbalance force which is generated in the chopper plate moved vertically by the arms united with the small gears is canceled out by use of counterweights. However, the masses of the intermediate gears and the small gears revolving about the respective center lines break the dynamically balanced state of the rotary motion system, so that vibration, resonation, and noise are generated as a result of play such as backlash of gears, and the durability of the apparatus is impaired.
(3) The above-described vibration propagates to the chopper blade via the arms, so that the chopper blade vibrates, resulting in breakage of signatures and decreased folding accuracy. Further, resonation, etc., caused by the vibration makes coping with increased operation speed of rotary presses difficult.
The above-described Conventional Apparatus 2 has the following drawbacks.
(1) Each of the two linear-feed crank mechanisms is designed such that two crank members are rotated in opposite directions through meshing engagement of two gears connected to the crank members. Further, the inner-side gears of the two linear-feed crank mechanisms located adjacent to each other are engaged, so that four gears are disposed along a horizontal line. Therefore, the apparatus is of relatively large side. In addition, as a result of backlash of gears and variation in load acting on the crank pin portions, vibration and noise are generated, so that the chopper blade vibrates and/or resonates.
(2) The chopper blade is supported by two pairs of links such that the distal ends of each pair of links are coaxially pin-connected to the corresponding end of the chopper blade. Therefore, the rigidity of the chopping blade is difficult to maintain, and therefore, the chopping blade vibrates easily. Therefore, the chopper blade moves upward and downward, while vibrating horizontally in the longitudinal direction of the chopper blade and in the direction perpendicular thereto, so that the accuracy in folding signatures is impaired, and the apparatus cannot cope with increased operation speed of rotary presses.
(3) The linear-feed crank mechanism is mainly formed of a considerably expensive gear box which includes a large number of components. In addition, since the crank members are rotated through mutual, direct engagement between gears provided on the rotary shafts of the crank members, backlashes of the gears are accumulated, resulting in generation of large play.
(4) High machining accuracy is required to obtain an accurate distance between the center of the rotary shaft of each crank member to the center of the corresponding crank pin and an accurate distance between the centers of pin connections at opposite ends of each link. Therefore, manufacturing cost is high, and theoretical or ideal dimensions cannot be obtained, so that the apparatus causes complicated motion with vibration. Further, excessive force is easily generated, because of dimensional errors of the respective members. When the clearance between movable members is increased so as to dissipate such excessive force, durability is impaired.
The above-described Conventional Apparatus 3 has the following drawbacks.
(1) Since the reciprocal linear-motion unit for moving the chopper blade upward and downward is realized by a planetary gear box including an internal gear and a small gear, the apparatus has a complex structure and is formed of considerably expensive components. Therefore, manufacturing cost is high.
(2) In order to move the chopper blade linearly, the pitch circle diameter of the small gear is set to be half the pitch circle diameter of the internal gear, and the crank radius is set to be half the pitch circle diameter of the small gear. As a consequence of these dimensional relationships, the chopper blade moves within a large stroke corresponding to the pitch circle diameter of the internal gear, resulting in an increase in the size of the apparatus.
(3) Moreover, as a consequence of the large stroke of the chopper blade, the speed of reciprocal motion of the guide portion for guiding the motion of the chopper blade along the direction of reciprocal linear motion increases, so that the bearings wear quickly, and excessive force acts on the crank pin engaged with the chopper blade, resulting in impaired durability.
(4) Further, as described above, difficulty is encountered in obtaining the theoretical or ideal dimensional relationship in relation to the gears and the crank radius through precise matching and assembly, as well as in operating and maintaining the apparatus to move the chopper blade precisely linearly. In actuality, the locus of motion of the crank pin deviates from a straight line. Therefore, the crank pin is engaged with an elongated hole formed in the chopper blade. However, since the crank pin and the elongated hole wear, durability is low. Further, vibration and resultant resonation lower folding accuracy and make coping with high speed operation difficult.
The above-described conventional apparatuses share the following common problems.
Notably, the numbers appearing in parentheses following each common problem below correspond to the numbered drawbacks listed above for the corresponding conventional apparatuses.
1. Generation of vibration and noise (Conventional Apparatus 1-(2); Conventional Apparatus 2-(1), (3), (4); Conventional Apparatus 3-(4)).
2. Low folding accuracy (Conventional Apparatus 1-(3); Conventional Apparatus 2-(2); Conventional Apparatus 3-(4)).
3. Impossibility of coping with high-speed operation (Conventional Apparatus 1-(4); Conventional Apparatus 2-(2); Conventional Apparatus 3-(4)).
4. Large apparatus size (Conventional Apparatus 1-(1); Conventional Apparatus 2-(1); Conventional Apparatus 3-(2)).
5. Low durability (Conventional Apparatus 1-(2); Conventional Apparatus 2-(4); Conventional Apparatus 3-(3), (4)).
6. High manufacturing cost (Conventional Apparatus 1-(1); Conventional Apparatus 2-(4); Conventional Apparatus 3-(1) .